The present invention relates generally to the field of battery post forming and/or burning, and more particularly, to the field of burning battery posts with battery cover bushings for the purpose of forming an integrally fused battery terminal on the outer surface of the battery case. This invention, therefore, relates to welding in general, and specifically, for welding battery terminal posts, as for example, the type of battery terminals used in automobile batteries.
In the welding of various members together, it is commonplace to use a welding rod having flux therein, for many types of welding, such as arc welding. In other instances, particularly when the materials being welded together are soft, such as those comprising pot metal, lead, lead alloys, or like materials, welding may be effected by application of open flame to members that are to be welded together. In many instances, such techniques are highly desired and quite meritorious, however, in some instances, as for example, when electrical conductivity is desired, it becomes paramount that the connection between members being welded be such as to create minimal electrical resistance.
In the manufacture of electric storage batteries, such as the lead acid batteries normally used in automobiles, groups of battery plates and separators contained in separate cells in a battery case are placed in the case, after which time the various cells are joined in any of a number of ways to form intercellular connections therebetween. At the end of the storage battery, slender battery posts which will form the positive and negative terminals of the battery extend above the upper surface of the open battery case. These battery cases, which are normally composed of polypropylene or other plastic material, are adapted to receive thereon a polypropylene battery cover, which has formed therein two lead bushings adapted to be pierced by the battery posts when the cover is fitted onto the top of the case. A liquid-tight seal is then formed between the battery case and battery cover, either by gluing, ultrasonic welding, or by heat sealing means, and the final mechanical assembly is completed by fusing the battery post elements with the battery cover bushing elements to produce the desired positive and negative battery terminals.
Following the burning of the battery bushing elements and battery post elements to form positive and negative terminals on the battery, acid filling, forming, and other operations, may be conducted in order to produce a finished battery. Consequently, the burning process for forming integral, leak-proof battery terminals is only one step in the assembly of the complete electric storage battery.
The present invention also relates to the art of producing intercellular connections between pluralities of cells within a battery. In each cell, there are disposed a plurality of parallel but spaced plates, each having a lug extending therefrom, with various lugs being interconnected by a battery strap, by any suitable means, such as that disclosed in U.S. Pat. No. 3,395,748. Extending from a strap of this type, which connects plates of a given cell, is a post. Adjacent cells in a given battery are separated by cell partitions. Posts or groups of plates and adjacent cells must be connected for electrical conductivity between the cells. Accordingly, it is also this connection of adjacent battery cell posts that is of interest in this application.
Because of the presence of the cell partition between the posts, the posts are somewhat spaced at their upper end, in that the posts extend generally upwardly above the height of the cell partitions, such upward extension or protrusion facilitating the application of heat thereto, for obtaining an electrical connection between the posts across the upper end of an associated plate. Because the necessity of obtaining good electrical conductivity across such post connections, the art of welding battery posts has become highly developed, with individuals for performing the same having developed a high degree of skill with respect thereto.
In welding battery posts, either during the fusing process with battery cover bushing elements or with adjacent posts, it is possible to use a gas-oxygen torch or the like, of an intensity which will permit the delivery of sufficiently high temperature to the elements to be joined, while at the same time preventing the material at the upper end of the posts closest to the flame from reaching excessive temperatures, such that early metal flow from the upper ends of the posts commences, such flow continuing down into the space between the posts and bushings and/or between the two posts above the separator plates, and solidifying there, before lower ends of the posts in the vicinity of the upper end of the separator plate and/or at the base of the bushings have become sufficiently heated, thereby resulting in an incomplete fusion of metal at a location corresponding to the base of the battery terminal to be formed and/or at the upper edge of the cell partition. Thus, the result is that while a good fusion may exist at the upper ends of the weld, often, at the lowermost ends of the weld the fusion is imperfect, with insufficient bond to provide sufficiently low electrical resistance as a connector. In order to avoid this, an operator may play the torch between the various elements to be welded, however, particularly in the case of the polypropylene battery cover, it is not possible to hold the torch in close proximity to that battery cover for fear that the battery cover will become scorched or damaged around its junction with the bushing. Accordingly, the results of welding battery terminals often results in variations or lack of uniformity in weldments, depending upon the particular operator or welder involved, as well as resulting in an undesirable percentage of rejects due to welds that have a sufficiently good external appearance to pass customary quality controls, but which are really poor weldments. Furthermore, since the appearance of battery terminals, unlike intercellular connections, are available for visual inspection by the intended consumer, even if a weld of high electrical integrity is formed by the process, the battery is likely to be rejected if the resulting battery terminal lacks a solid, uniform appearance.